Fluorinated compounds such as hydrofluoroolefins are produced via fluorination or dehydrofluorination reactions of hydrofluorocarbons, hydrochlorocarbons or hydrochlorofluorocarbons. These reactions are generally carried out in the presence of hydrofluoric acid (HF) as fluorination agent. For example, WO2013/088195 describes the preparation of 2,3,3,3-tetrafluoropropene.
During these reactions, hydrochloric acid is produced. The latter may be separated from the other products of the reaction via a distillation column, in order ultimately to recover the hydrochloric acid without fluorinated impurities. Indeed, the hydrochloric acid recovered in gaseous form is subsequently absorbed in water in order to produce aqueous hydrochloric acid solutions which must have a low content of fluorinated products.
Aside from hydrochloric acid, light organic impurities may also be formed during fluorination reactions. Especially during the production of 2,3,3,3-tetrafluoropropene (1234yf), the light organic impurities are for example trifluoropropyne, trifluoromethane, pentafluoroethane, chloropentafluoroethane or 1,1,1-trifluoroethane. These light organic impurities are extracted from the desired product during purification thereof, via a distillation column intended for this purpose. The removal of these light organic impurities is generally accompanied by a loss of the desired product, the boiling point of which is often close to that of the light organic impurities. This may therefore reduce the overall yield of the process. Typically, the loss of the desired product due to the intermediate distillation of the light organic impurities is approximately 5%.
There is therefore still a need to employ a fluorination process that makes it possible to minimize losses of the desired product during the process for the purification thereof.